1. Field of the Invention
The present invention relates to a cleaning device for cleaning an intermediate transferring member in an image-forming apparatus, such as a copying machine, a facsimile and a laser printer, of an electro-photographic system that forms monochrome images or color images, and an image-forming apparatus provided with such a cleaning device.
2. Description of the Related Art
The intermediate transferring member is a member that is used for holding a toner image primarily transferred from a surface of a photosensitive member onto its surface, and allowing the image to be secondarily transferred on a recording medium such as a sheet of paper after transporting the toner image in an image-forming apparatus. Since objects to be cleaned such as residual toner, toner external additives, powder of recording medium and filling materials of recording medium, are present on the surface of the intermediate transferring member, the image-forming apparatus is provided with a cleaning device for cleaning and removing the objects to be cleaned from the surface of the intermediate transferring member.
As such a cleaning device, for example, Japanese Patent Application No. 2002-229344 has proposed an intermediate transferring belt cleaning device as shown in FIG. 6. More specifically, the device includes a first cleaning brush 151A and a second cleaning brush 151B, and a positive bias voltage is applied to the first cleaning brush 151A and a negative bias voltage is applied to the second cleaning brush 151B. Thus, the negative toner of the residual toner on an intermediate transferring belt 104 is collected by the first cleaning brush, and one portion thereof is positively charged. The positive toner can be cleaned by the second cleaning brush.
However, in the case when an amount of residual negative toner on an intermediate transferring belt increases, the toner, which is neither collected by the first cleaning brush, nor positively charged, increases to cause toner that cannot be collected even by the second cleaning brush. For this reason, by increasing a density of planted brush hairs, contact portions with the toner are increased; however, although cleaning performance is enhanced, the effect was not sufficient. Since the first cleaning brush has a higher possibility of contact with the toner than the second cleaning brush, the toner is retained in the first cleaning brush. As a result, it is not possible to solve the problem of degradation of cleaning performance with time.
In the case when a cleaning operation on the intermediate transferring belt becomes insufficient, such toner retained on the intermediate transferring belt and continuously turned around, and also fixed to the belt (to cause filming) is generated. When the filming occurs, smoothness and conductive property of the belt surface deteriorate, failing to obtain a good transferring function to cause degradation of image quality.